System and process for treatment and de-halogenation of ballast water

ABSTRACT

A system and process for de-halogenating ballast water before releasing the ballast water from the vessel. In one embodiment, the system comprises a means for measuring the halogen content of the ballast water, a reducing agent source in fluid communication with the ballast water, and a means for controlling the amount of reducing agent supplied to the ballast water. In one aspect, the means for measuring the halogen content comprises one or more oxidation/reduction potential analyzers. In another embodiment, the system comprises one or more hypochlorite electrolytic cells for generating hypochlorite to treat the ballast water. 
     One embodiment of the process for de-halogenating ballast water comprises measuring the oxidation/reduction potential of the ballast water and adding one or more reducing agents to the ballast water to de-halogenate the ballast water in response to the measured oxidation/reduction potential. In one aspect, the oxidation/reduction potential is modulated so that excess reducing agent is present in the ballast water.

PRIORITY CLAIM

This application is a Continuation-in-Part of U.S. application Ser. No.11/037,642, filed Jan. 18, 2005

FIELD OF THE INVENTION

The system and process of this invention relate generally to a systemand process for the treatment of ballast water to eliminate marinespecies and pathogenic bacteria from ballast water. More particularly,the system and process of this invention treats ballast water withhypochlorite produced on-site.

BACKGROUND OF THE INVENTION

Ballast water is used to balance the weight distribution in a marinevessel. Ballast water is pumped into tanks where it is stored toproperly balance a vessel for a voyage. Often ballast water is taken onat one port and transported to another where it is emptied into the newport. This common practice has an inherent danger. Releasing the ballastwater taken aboard from a distant location can be both harmful to theenvironment and dangerous to human and animals in a new port.

The introduction of non-native marine life into a new ecosystem can havea devastating effect on the native flora and fauna which may not havenatural defenses to the new species. Additionally, harmful bacterialpathogens, such as cholera, may be present in the origination pod. Thesepathogens can multiply in the ballast tanks over time and cause anoutbreak of illness in the area where they are released.

The dangers posed by the marine life and pathogens may be controlled bykilling those species present in the ballast water. For the pastcentury, chlorination has become the standard way to disinfect watersupplies, potable water, wastewater and swimming pools, for example, toeliminate epidemics of waterborne diseases.

SUMMARY OF THE INVENTION

The present invention provides a system and method for treating ballastwater in a marine vessel. Ballast water is piped onto a vessel in oneport or harbor and discharged upon reaching another port. On-sitehypochlorite generation allows the ballast water to be treated on boardthe vessel before the ballast water is released in a distant port.Treating the ballast water with hypochlorite generated from the ballastwater itself or an alternate salt water source eliminates many of themarine organisms and bacteria which may be transported from the firstport and propagated within the ballast water tanks. The elimination ofthese organisms in turn eliminates the introduction of non-native marinespecies into the water, and prevents outbreaks of water born diseasessuch as cholera.

Halogens in the form of halogen-containing oxidizing agents, such asHOCl and HOBr, are produced by hypochlorite generation and intended tokill organisms in ballast water onboard a vessel. When the ballast watercontaining the halogens is released from the vessel thehalogen-containing oxidizing agents are potentially dangerous to themarine flora and fauna around the vessel.

In one embodiment of the system of the invention the system comprises ade-halogenation system to remove the halogens from the ballast water.De-halogenating the ballast water comprises neutralizing the oxidizingagents to form the neutral salts of the halogens. The de-halogenationsystem comprises a means for measuring the halogen content of theballast water, a reducing agent source in fluid communication with theballast water, and a means for controlling the amount of reducing agentsupplied to the ballast water. The means for controlling the amount ofreducing agent is in communication with the means for measuring thehalogen content.

In one aspect of the de-halogenation system, the means for measuring thehalogen content of the ballast water can comprise one or moreoxidation/reduction potential analyzers for determining theoxidation/reduction potential of the ballast water.

In another aspect of the de-halogenation system, the reducing agentsource can comprise a reducing agent tank and a pump in fluidcommunication with the reducing agent tank. The pump is in communicationwith the means for controlling the amount of reducing agent.

In an additional aspect, the reducing agent source can comprise anycombination of suitable reducing agents. Examples of suitable reducingagents include sodium sulfite, sodium metabisulfite, sodium bisulfite,sulfur dioxide, and sodium thiosulfate.

In another embodiment of the de-chlorination system, the system furthercomprises a means for verifying the effectiveness of the de-halogenationof the ballast water.

In an additional embodiment, the system for treating ballast water ofthe present invention comprises one or more hypochlorite electrolyticcells and a de-halogenation system. The hypochlorite electrolytic cellsare in fluid communication with a salt water source and one or moreballast water tanks. The de-halogenation system is in fluidcommunication with the ballast water tanks.

In another embodiment, the system for treating ballast water furthercomprises a means for discharging the ballast water from the ballastwater tanks. In one aspect, the means for discharging the ballast waterfrom the ballast water tanks can comprise one or more discharge pumps influid communication with the ballast water tanks and discharge piping influid communication with the discharge pumps. The discharge pipingdefines a discharge opening to outside of the vessel. Thede-halogenation system can be in fluid communication with the means fordischarging the ballast water from the ballast water tanks.

In additional embodiments of the system for treating ballast water, thesystem can comprise any combination of a means for controllinghypochlorite generation, a flow meter for measuring ballast water flowrate, a total organic carbon analyzer for measuring total organic carboncontent of the ballast water, a means for verifying the effectiveness ofthe ballast water treatment, and a means for verifying the effectivenessof the de-halogenation of the ballast water.

In one embodiment of the process of this invention, the processcomprises de-halogenating the ballast water onboard a vessel bymeasuring the oxidation/reduction potential of the ballast water. One ormore reducing agents are added to the ballast water to de-halogenate theballast water in response to the measured oxidation/reduction potential.In one aspect, the amount of reducing agent added to the ballast watercan be modulated to maintain an oxidation/reduction potentialmeasurement that indicates excess reducing agent is present in theballast water. In another aspect, the oxidation/reduction potential canbe maintained at less than about 200 mV. In still another aspect, theoxidation/reduction potential is maintained at about 0 mV.

The oxidation/reduction potential of the ballast water can be measuredat any suitable site. Examples of suitable sites include within the oneor more ballast water tanks, downstream from the ballast water tanks,upstream from one or more ballast water discharge pumps, downstream fromthe ballast water discharge pumps, prior to the addition of reducingagent, and after the addition of reducing agent.

In additional embodiments of the de-halogenation process, the processcan further comprise any combination of recording theoxidation/reduction potential of the ballast water at timed intervals,providing the recorded oxidation/reduction potentials to a regulatoryagency, and removing the recorded oxidation/reduction potentials with aportable data recording device.

In a further embodiment, the process comprises treating the ballastwater with generated hypochlorite and de-halogenating the ballast water.The process comprises drawing ballast water onboard a vessel and feedingthe ballast water to one or more ballast tanks. Salt water from a saltwater source is piped to the one or more hypochlorite electrolyticcells. An amperage is applied to the one or more hypochloriteelectrolytic cells to produce hypochlorite within the salt water. Thesalt water comprising hypochlorite is introduced to the ballast water.The halogen content of the ballast water is measured with a means formeasuring halogen content. Reducing agent is added to the ballast waterin response to the measured halogen content to de-halogenate the ballastwater prior to discharge from the vessel.

In one aspect, the salt water source comprises a side stream removedfrom the ballast water. In another aspect, the means for measuringhalogen content comprises one or more oxidation/reduction potentialanalyzers.

In another embodiment, the process for treating ballast water furthercomprises measuring the oxidation/reduction potential of the ballastwater and adding a reducing agent to the ballast water to de-halogenatethe ballast water in response to the measured oxidation/reductionpotential. The ballast water is then discharged from the vessel. In oneaspect, the amount of reducing agent added to the ballast water ismodulated to maintain an oxidation/reduction potential measurement thatindicates excess reducing agent is present in the ballast water. Inanother aspect, the process further comprises measuring and recordingthe oxidation reduction potential of the combined ballast water and sidestream to confirm that excess halogen is present. Optionally, residualhalogen can be maintained at a concentration of at least 1 ppm.

In a further embodiment, the process further comprises measuring andrecording process data. Examples of process data which may be recordedinclude ballast water flow rate, amperage applied to the hypochloriteelectrolytic cells, voltage of the hypochlorite electrolytic cells,oxidation/reduction potential of the ballast water and side streamcombined, and oxidation/reduction potential of the ballast water priorto discharge from the vessel.

In additional embodiments, the amount of hypochlorite generated may becontrolled by modulating the amperage applied to the hypochloriteelectrolytic cells. The hypochlorite generated may be controlled inresponse the measured flow rate of the ballast water or the totalorganic carbon content of the ballast water. In another aspect, theamount of hypochlorite generated can be controlled to ensure that excesshalogen exists in the ballast water.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of this invention's system for treating ballastwater.

FIG. 2 is a schematic of this invention's system for neutralizingchlorine.

FIG. 3 is a chart showing the experimental results of treating ballastwater with the system and method of this invention.

FIG. 4 is another chart showing the experimental results of treatingballast water with the system and method of this invention.

FIG. 5 is a schematic of one embodiment of the system for treatingballast water.

FIG. 6 is a schematic of one embodiment of the system forde-halogenating ballast water.

DETAILED DESCRIPTION

The present invention provides a system and process for treating ballastwater. One preferred on-site reaction for creating sodium hypochlorite(NaOCl) is illustrated in the following equation:NaCl+H₂O+2e ⁻→NaOCl+H₂↑

Referring to FIG. 1, in one preferred embodiment of the invention inwhich the ballast water is treated on-site, water is pumped on board amarine vessel, a ship or oil rig, for example. The water is eitherseawater with natural salt content or freshwater. In one embodiment, aside stream of ballast water is separated from the main water streamgoing to the ballast tanks 170. In an alternative embodiment, the sidestream is drawn from the ballast water tanks 170 after the main ballastwater stream has entered the ballast water tanks 170. The side streamflows through the side stream piping 100 to one or more hypochloriteelectrolytic cells 130 where hypochlorite is generated either from thesalt naturally present in the ballast water, if seawater, or from addedchloride salts if fresh water. Seawater is used for the purposes of thisdescription, but this invention is not limited to seawater. Anychlorine-generating salt water may be used.

The one or more electrolytic cells are equipped with electrodesenergized under direct anodic and cathodic current. In this conditionpartial electrolysis of sodium chloride (NaCl) contained in raw seawateroccurs. The aqueous solution of sodium chloride (NaCl), which iscompletely dissociated as sodium ion (Na+) and chlorine ion (Cl⁻),reacts at the anode to generate free chlorine. The hydroxide ions (OH⁻)in the water migrate from the cathodic area and react with Na+ and Cl₂near the anode to produce sodium hypochlorite (NaOCl) and hydrogen (H₂).

Sodium hypochlorite in water hydrolyzes to form hypochlorous acid(HOCl). Some of the HOCl reacts with the bromine in the water to formhypobromous acid (HOBr). HOCl and HOBr act as the killing agents used totreat the ballast water.

In one aspect, the water can then flow into a hydrogen separator 140where the hydrogen byproduct (H₂) of the hypochlorite generation isseparated from the side stream. The side stream is then reintroduced tothe ballast water stream to kill marine organisms and bacteria in theballast water tanks.

In one embodiment of the invention, the hydrogen separator 140 cancomprise a hydrocyclone separator. The hydrogen separator 140 can alsocomprise a means for venting hydrogen to the atmosphere 145.Additionally, the hydrogen separator 140 can comprise a tube with apressure relief valve to allow the hydrogen to separate from the liquid.Separating hydrogen from the water stream is important, as hydrogen ishighly flammable. Hydrogen is flammable in air in concentrations as lowas 4.1% and as high as 74%. Without the use of a hydrogen separator 140,it is possible for hydrogen to be introduced into the ballast watertanks where it could potentially reach hydrogen-air concentrations inthe flammability range.

One hydrocyclone separator 140 of this invention comprises a cylindricaltop section and a conical bottom section. Water from the one or moreelectrolytic cells, containing hydrogen, enters the side of the topsection. The hydrogen exits the top of the separator, while the waterexits the bottom. The water enters tangentially to the side of thecylindrical section so that the water travels in a circular path aroundthe cylindrical and conical sections before flowing out the bottom ofthe separator, facilitating the separation of the water and hydrogen.

In another embodiment of the invention, a chlorine analyzer 150, influid communication with the ballast water stream, measures the chlorinecontent of the ballast water. The chlorine analyzer 150 can bepositioned downstream from the one or more electrolytic cells 130. Inone aspect, the chlorine analyzer 150 is positioned downstream from thepoint where the chlorinated side stream (treatment stream) reenters theballast water stream. The chlorine analyzer 150 may further comprise asampling unit that modulates the hypochlorite content in ballast waterby measuring the chlorine level in the water and emitting a signal tothe electrolytic cells 130 to adjust the amount of hypochloritegenerated in the side stream relative to a predetermined concentrationin the ballast tank and piping. The chlorine analyzer 150 functions bytaking a sample and mixing it with an acidic iodide or potassium iodidereagent. The chlorine present in the sample oxidizes the iodide toiodine. The liberated iodine is measured by a membrane-covered,amperometric type sensor. The level of iodine is proportional to thetotal chlorine concentration in the sample.

Referring now to FIG. 5, an alternative embodiment of the systemcomprises a total organic carbon analyzer. In this embodiment, thesystem for treating ballast water comprises one or more hypochloriteelectrolytic cells 130 in fluid communication with a salt water source400. The salt water source can be a side stream 416 of the ballast waterdrawn onboard the vessel, water already in the ballast water tanks 220,a sea chest, a separate salt water tank, or any other source. Thehypochlorite electrolytic cells 130 are also in fluid communication withthe ballast water 402. Hypochlorite produced within the salt water bythe hypochlorite electrolytic cells 130 is added to the ballast water.This addition can be made either in the stream of ballast water drawnonboard the vessel, directly to the ballast tanks, or at any othersuitable location.

A total organic carbon analyzer 403 is also in fluid communication withthe ballast water 402. A total organic carbon (TOC) analyzer 403 is adevice which measures the concentration of carbon in water from organicsources, such as microorganisms, plant materials, algae, humicmaterials, organic acids, and mineral compounds of organic origin. Totalorganic carbon analyzers are available from the manufacturers O.I.Analytical and HATCH instruments. As a general rule, it is known in theart that about 1 ppm of chlorine is required to neutralize about 1 ppmof TOC.

The system further comprises a means for controlling hypochloritegeneration 404 in communication with the total organic carbon analyzer403. While the means for controlling hypochlorite generation 404 cancomprises any suitable equipment, in one embodiment it comprises acontrol system 405 in communication with the total organic carbonanalyzer 403 and a power source 406 that is electrically connected tothe hypochlorite electrolytic cells 130. The control system 405 canadjust the amperage applied to the hypochlorite electrolytic cells 130in response to the TOC measurement.

In another embodiment, the system further comprises a flow meter 407 influid communication with the ballast water 402. The flow meter 407 is incommunication with the means for controlling hypochlorite generation404. The flow meter 407 can be placed in the ballast water stream drawnonboard the vessel to measure the ballast water flow rate. The means forcontrolling hypochlorite generation 404 can utilize the ballast waterflow rate and the TOC measurement to determine the amount ofhypochlorite required to be generated to kill the organisms in theballast water and thus the amperage that must be applied to thehypochlorite electrolytic cells 130 to generate the hypochlorite.

In yet another embodiment, the system comprises an oxidation/reductionpotential analyzer 408 in addition to the TOC analyzer. In general, anoxidation/reduction potential (ORP) analyzer measures voltage across acircuit formed by a reference electrode and a measurement electrode,with the subject solution between the electrodes. Theoxidation/reduction potential of the ballast water is relative to theconcentration of the HOCl and HOBr oxidizing agents in the ballastwater. Both HOCl and HOBr are oxidizing agent forms of halogens chlorineand bromine. Oxidizing agents steal electrons from the unwanted plantsand animals in the ballast water, altering their chemical makeup andkilling them. The oxidation/reduction potential analyzer is in fluidcommunication with the ballast water. The ORP analyzer 408 communicatesthe oxidation/reduction potential to the means for controllinghypochlorite generation 404. When the OPR analyzer 408 is placeddownstream from the point of addition 409 of the hypochlorite to theballast water, the means for controlling hypochlorite generation 404 canuse the measurement to confirm the existence of excess halogen in theform of an oxidizing agent in the ballast water to ensure that enoughhypochlorite is present to kill all microorganisms in the ballast water.

In still another embodiment, the system comprises a means for recordingsystem data 410. The means for recording system data 410 can compriseany data recording equipment known in the art. Examples of such datarecording equipment include computerized equipment, such as hard drivesflash memory, CD-ROM's, and magnetic disks, as well as non-computerizedrecording equipment, such as paper plots. System data to be recorded caninclude any data desirable to one skilled in the art, including but notlimited to, ballast water flow rate, amperage applied to and cellvoltage of the hypochlorite electrolytic cells 130, oxidation/reductionpotential of the ballast water 402 and side stream 416 combined, andoxidation/reduction potential of the ballast water prior to dischargefrom the vessel.

In a further embodiment, the system can comprise a means for verifyingthe effectiveness 411 of the ballast water treatment. The means forverifying the effectiveness of the ballast water treatment can beincluded within the means for recording system data 410 or the means forcontrolling hypochlorite generation 404. The means for verifying theeffectiveness of the ballast water treatment can comprise any meansknown in the art to demonstrate to a regulatory authority, such as theCoast Guard or Port Authority, that ballast water treatment was properlyperformed, including but not limited to, a plot of system data, aremovable hard drive or flash drive, downloading system data on a laptopcomputer or a handheld device, transferring system data over theinternet, or wirelessly transmitting system data to an off vessellocation. The regulatory authority may use this information to confirmthat the ballast water was properly treated.

In still a further embodiment, the system comprises one or more ballastwater tanks 220 and a means for discharging 412 the ballast water fromthe ballast tanks 220. The means for discharging 412 the ballast watercan comprise any suitable combination of pumps, siphons, and piping toremove the ballast water from the ballast tanks and the vessel. In oneaspect, the means for discharging 412 the ballast water from the ballasttanks 220 comprises one or more discharge pumps 413 in fluidcommunication with the ballast tanks 220, discharge piping 414 in fluidcommunication with the discharge pumps 413, and a discharge opening 415to outside the vessel.

In an additional embodiment, the system can comprise a means forde-halogenating 417 the ballast water. The means for de-halogenating 417the ballast water can comprise a sulfite auxiliary system 200 or ade-halogenation system 500. For the purposes of this invention,“de-halogenation” means neutralization of the oxidizing agent form ofthe halogen.

Referring again to FIG. 1, in another alternative embodiment of thisinvention, a filter 180 is present and in fluid communication with theballast water stream. The filter can be positioned upstream from theside stream leading to the one or more electrolytic cells to removedebris from the side stream. The filter is preferably a 50-micronself-cleaning filter. A self-cleaning filter measures the pressuredifferential across the filter. As the filter screen becomes cloggedwith the debris removed by the filter, the pressure differentialincreases. Once the pressure differential reaches a certain setpoint ora predetermined amount of time has lapsed, the filter screen is cleanedby a suction scanner with nozzles that spiral across the inner surfaceof the screen. The filtration debris is vacuumed from the screen andexpelled out the exhaust valve.

In another embodiment of the invention, the hypochlorite electrolyticcell comprises a tubular cell. The tubular cell comprises an outermonopolar tube and inner bipolar tube. The hypochlorite electrolyticcell can also comprise other types of electrolytic cells. Many types ofhypochlorite electrolytic cells are known within the onsite,electrochlorination industry. Other types of electrolytic cells includea plate type hypochlorite generator. The electrolytic cell is selectedbecause of its configuration of connection nodes to the electrodes andthe hydraulic flow of liquid throughout the cell.

In still another embodiment of the invention, a booster pump 110 isconnected to the side stream piping 100 to increase the pressure ofwater through the ballast water treatment system. Increased pressure isnecessary because a substantial pressure drop occurs as the side streampasses through the hypochlorite electrolytic cells 120, which must becompensated for in order to allow the side stream to be reintroducedinto the ballast water stream. The booster pump 100 can be positionedeither upstream or downstream from the hypochlorite electrolytic cells120.

Ballast water is typically taken aboard in one port or harbor and thenreleased at the next harbor. Residual halogens, like chlorine andbromine in the form of oxidizing agents HOCl and HOBr, in the ballastwater tanks that is not consumed in the treatment of the ballast wateris potentially harmful to the marine ecosystem in the new harbor wherethe ballast water is discharged. The residual chlorine could kill nativeflora and fauna in the ecosystem. Consuming or neutralizing thisresidual chlorine immediately prior to discharging the ballast waterprotects against damage which the residual chlorine would cause. In oneembodiment of the invention, a de-chlorination system 200 can be addedto neutralize residual chlorine in the ballast water tank 170 before theballast water is released from the vessel into the port, ocean, lake, orriver. The de-chlorination system can be positioned downstream from theballast tanks. In one embodiment illustrated in FIG. 1, thede-chlorination system can comprise a sulfite auxiliary system. Thesulfite auxiliary system 200 can comprise a sulfite tank 210, a pump220, and a sulfite analyzer 230. In one aspect, the pump of the sulfiteauxiliary system 200 is a diaphragm-metering pump. The diaphragmmetering pump controls the flow of sulfite used to neutralize residualchlorine.

The sulfite auxiliary system 200 removes residual chlorine by reactingthe chlorine with sulfur dioxide gas, a solution of sodium bisulfite, orsodium sulfite. The residual chlorine is consumed in the followingreaction,Na₂SO₃+Cl₂+H₂O→Na₂SO₄+2HClSo long as excess sulfite ions are present in the effluent, effectivelyno chlorine is present. The sulfite analyzer converts the sulfite ionsin the treated water sample to sulfur dioxide by mixing the sample withacid. The sulfur dioxide is then stripped from the sample and measuredby a gas sensor. The analyzer 230 provides a control output to controlthe feed from the sulfite tank to de-chlorinate the ballast waterstream.

Alternatively, as shown in FIG. 6 a de-halogenation system 500 can beemployed for de-halogenating ballast water. Halogens, including chlorineand bromine in the form of oxidizing agents HOCl and HOBr, arepotentially hazardous to marine life if released from the vessel.De-halogenating the ballast water comprises neutralizing oxidizing agentforms of the halogens to create neutral salt derivatives of the halogenswhich are no longer oxidizing agents. The de-halogenation systemcomprises a means for measuring the halogen content 502 of the ballastwater, a reducing agent source 501 in fluid communication with theballast water, and a means for controlling the amount of reducing agent503 supplied to the ballast water. The means for controlling the amount503 of reducing agent is in communication with the means for measuringthe halogen content 502.

The means for measuring halogen content 502 can comprise one or moreoxidation/reduction potential analyzers, one or more chlorine analyzers,or wet chemical analysis with potassium iodine indicator and sodiumthiosulfate titration. The means for controlling the amount of reducingagent 503 can comprise any combination of equipment known in the art,including, but not limited to, a control system, a computer, aprogrammable logic controller, and a pump.

In one aspect, the reducing agent source 501 can comprise a reducingagent tank 505 and a pump 504 in fluid communication with the reducingagent tank 505. The pump 504 is in communication with the means forcontrolling the amount of reducing agent 503. Suitable pumps include avariable dosing pump.

In another aspect, the reducing agent source 501 can comprise one ormore suitable reducing agents. Examples of suitable reducing agentsinclude sodium sulfite, sodium metabisulfite, sodium bisulfite, sulfurdioxide, and sodium thiosulfate.

In still another aspect, the de-halogenation system 500 comprises ameans for verifying the effectiveness of the de-halogenation 506 of theballast water. The means for verifying the effectiveness of thede-halogenation 506 of the ballast water can comprise any means known inthe art to demonstrate that the ballast water was properlyde-halogenated, including, but not limited to, a plot of system data, aremovable hard drive or flash drive, downloading system data on a laptopcomputer or a handheld device, transferring system data over theinternet, or wireles sly transmitting system data to an off-vessellocation. Optionally, the means for verifying the effectiveness of thede-halogenation 506 can be included in the means for controlling amountof reducing agent 503. A regulatory authority can use this data toconfirm that the ballast water was properly de-halogenated.

In another embodiment of the system for treating ballast water, thesystem comprises one or more hypochlorite electrolytic cells 130 influid communication with a salt water source 400 and one or more ballastwater tanks 220, and a de-halogenation system 500 in fluid communicationwith the ballast water tanks 220. In one embodiment, salt water source400 can be a side stream 416 of the ballast water drawn onboard thevessel.

In one aspect, the system can comprise a means for discharging 412 theballast water from the ballast tanks. In one embodiment, the means fordischarging 412 the ballast water from the ballast tanks 220 comprisesone or more discharge pumps 413 in fluid communication with the ballasttanks 220, and discharge piping 414 in fluid communication with thedischarge pumps 413. The discharge piping 414 can define a dischargeopening 415 to allow the ballast water to be removed from the vessel. Inanother aspect, the de-halogenation system 500 is in fluid communicationwith the means for discharging 412 the ballast water from the ballasttanks.

In yet another aspect, the system can further comprise a means forcontrolling hypochlorite generation 404. Additionally, the system cancomprise a flow meter 407 for measuring ballast water flow rate. Theflow meter is in communication with the means for controllinghypochlorite generation 404.

In still another aspect, the system can further comprise a means forverifying the effectiveness of the ballast water treatment 410. Thesystem can also comprise a means for verifying the effectiveness of thede-halogenation 506 of the ballast water. Optionally, both the means forverifying the effectiveness of the ballast water treatment 410 and themeans for verifying the effectiveness of the de-halogenation 506 of theballast water can be included within the means for controlling thehypochlorite generation 404.

In one embodiment of a method of this invention, ballast water istreated by first drawing a ballast water stream on board the vessel. Theballast water stream may then be filtered. A portion of the filteredballast water stream is drawn off through the side stream piping 100 toform a treatment stream. This treatment stream is piped to hypochloriteelectrolytic cells, where a current is applied to the cells to producehypochlorite within the treatment stream. Hydrogen, which is flammable,is separated from the treatment stream before the treatment stream isreintroduced into the main ballast water stream. The ballast waterstream containing the hypochlorite is sampled after the treatment streamis reintroduced to the ballast water stream to determine the chlorineconcentration of the ballast water stream.

In one aspect of the method of this invention, the treatment stream isremoved from the ballast water stream before the stream enters theballast water tank. Alternatively, the treatment stream is drawn off ofthe ballast water tanks. The treatment stream is then treated withhypochlorite and reintroduced into the ballast water stream before thestream enters the ballast water tank. The hypochlorite electrolyticcells use natural salt water when the ballast water tanks take onseawater, to generate hypochlorite in the treatment stream.Alternatively, if fresh water is used as ballast water, a sodiumchloride salt can be added to the fresh water to supply the chlorideion.

In an alternative embodiment of the method, the pressure of thetreatment stream, which drops as the stream enters the side streampiping 100, is increased with a pump. In another preferred embodiment ofthe method, the ballast water stream is filtered prior to entering thetreatment stream. In another embodiment of the method, hydrogen isseparated from the treatment stream by a hydrocyclone separator.

In another embodiment of the method, the ballast water stream is sampledafter the treatment stream is reintroduced into the ballast water todetermine the chlorine concentration of the ballast water stream. Thechlorine concentration of the ballast water stream is measured by achlorine analyzer. The current in the hypochlorite electrolytic cells isadjusted in response to the measured chlorine concentration to increaseor decrease the hypochlorite generated in the treatment stream toachieve the proper concentration of hypochlorite in the ballast watertank.

In one embodiment of the process of this invention, the process fortreating ballast water comprises ascertaining the total organic carboncontent of the ballast water. The total organic carbon content can beascertained in any suitable manner including measuring with a totalorganic carbon analyzer, obtaining a value from a reference source, andsampling the ballast water and measuring TOC content with analyticalequipment. When measuring the total organic carbon content of theballast water, a measurement or sample can be taken at any suitablelocation, including in the incoming ballast water, the water outside thevessel, and the water in the ballast tanks.

To generate hypochlorite, salt water from a salt water source 400 ispiped to one or more hypochlorite electrolytic cells 100. In one aspectof the process, the salt water source can be a side stream 416 of theballast water drawn onboard the vessel. An amperage is applied to theone or more hypochlorite electrolytic cells to produce the hypochloritewithin the salt water. The salt water comprising hypochlorite isintroduced to the ballast water to treat the ballast water. In oneembodiment, the hypochlorite is introduced to the ballast water upstreamof the ballast water tanks to facilitate mixing of the hypochlorite andballast water. Hypochlorite production by the hypochlorite electrolyticcells is modulated in response to the total organic carbon content ofthe ballast water. The higher the TOC content of the ballast water thegreater the amount of hypochlorite that must be produced.

In another embodiment of the process, the step of modulatinghypochlorite production by the hypochlorite electrolytic cells inresponse to the total organic carbon content comprises adjusting theamperage applied to the hypochlorite electrolytic cells. Increasingamperage results in increased hypochlorite production. In one aspect,hypochlorite production is modulated to maintain residual halogen in theballast water. Residual halogen is halogen-containing oxidizing agent inexcess of the amount required to kill all the microorganisms present inthe ballast water. The presence of residual halogen in the ballast waterensures that no microorganisms remain in the ballast water that canmultiply in the ballast water tanks. In another aspect, hypochloriteproduction by the hypochlorite electrolytic cells in modulated so thatthe weight ratio of hypochlorite in the ballast water to total organiccarbon in the ballast water ranges from about 1.0 to about 3.0. A weightratio greater than 1.0 should maintain residual halogen in the ballastwater.

In an additional embodiment of the process, ballast water is drawnonboard the vessel and the flow rate of the ballast water is measured.The flow rate is combined with the TOC content of the ballast water todetermine a hypochlorite generation rate required to treat the ballastwater.

In one aspect of the process, process data can be measured and recorded.Examples of process data include total organic carbon content of theballast water, ballast water flow rate, amperage applied to thehypochlorite electrolytic cells, oxidation/reduction potential of theballast water and salt water comprising hypochlorite combined, andoxidation/reduction potential of the ballast water prior to dischargefrom the vessel.

In still another aspect of the process, residual halogen in the ballastwater produced by the electrolytic cells in response to the TOC contentcan be removed by de-halogenating the ballast prior to discharge fromthe vessel.

In an alternative method of this invention, ballast water is treated bydrawing a ballast water stream onto a marine vessel, filtering theballast water stream, and removing a portion of the filtered ballastwater stream to form a treatment stream. The pressure of the treatmentstream is increased. The treatment stream is then piped to hypochloriteelectrolytic cells, where a current is applied to the cells to producehypochlorite within the treatment stream. Hydrogen is separated from thetreatment stream by a means for venting. The treatment stream isreintroduced into the ballast water stream. The ballast water stream issampled after the treatment stream is reintroduced to determine thechlorine concentration of the ballast water stream. The current in theone or more hypochlorite electrolytic cells is adjusted in response tothe measured concentration to increase or decrease the hypochloritegenerated in the treatment stream. The treated ballast water stream canthen piped to the ballast tanks. Finally, prior to discharge, residualchlorine is neutralized in the ballast water stream downstream from theone or more hypochlorite electrolytic cells with sulfite.

In one embodiment of the method, hydrogen is separated from thetreatment stream by a hydrocyclone separator. Alternatively, the meansfor venting hydrogen can comprise venting the ballast water tanks to theatmosphere.

In another embodiment of the method, the step of neutralizing residualchlorine comprises piping the ballast water stream to a sulfiteauxiliary system. The sulfite auxiliary system is positioned downstreamfrom the ballast water tanks.

Residual halogens in the ballast water, such as chlorine and bromine,are potentially hazardous to marine life. In an alternative tode-chlorination as described, the ballast water can be de-halogenatedprior to its release from the vessel to eliminate the danger caused bythe residual halogen. The process for de-halogenating the ballast watercomprises measuring the halogen content of the ballast water with ameans for measuring halogen content 503. Reducing agents are added tothe ballast water in response to the measured halogen content tode-halogenate the ballast water prior to discharge from the vessel. Inone aspect, the reducing agent may be added downstream from the ballastwater tank. Examples of suitable reducing agents include sodium sulfite,sodium metabisulfite, sodium bisulfite, sulfur dioxide, sodiumthiosulfate, and combinations thereof.

In one embodiment, the process for de-halogenating ballast water onboarda vessel comprises measuring the oxidation/reduction potential of theballast water. One or more reducing agents are added to the ballastwater to de-halogenate the ballast water in response to the measuredoxidation/reduction potential. In one aspect, the amount of reducingagent added to the ballast water can be modulated to maintain anoxidation/reduction potential measurement that indicates excess reducingagent is present in the ballast water. When excess reducing agent ispresent, potentially harmful halogens like chlorine and bromine shouldnot be present. In another aspect, the oxidation/reduction potential ismaintained at less than about 200 mV. An OPR of less than 200 mVindicates that excess reducing agent exists. In still another aspect,the oxidation/reduction potential is maintained at about 0 mV.

Examples of suitable sites for measuring oxidation/reduction potentialinclude within the one or more ballast water tanks 220, downstream fromthe ballast water tanks 220, upstream from one or more ballast waterdischarge pumps 413, downstream from the ballast water discharge pumps413, prior to the addition of reducing agent, after the addition ofreducing agent, and combinations thereof. In another embodiment of theprocess, the oxidation/reduction potential of the ballast water can berecorded at timed intervals. The recorded oxidation/reduction potentialscan be monitored to confirm that de-halogenation was preformed properly.Optionally, the recorded oxidation/reduction potentials may be providedto a regulatory agency. In another aspect, the recordedoxidation/reduction potentials can be removed from the vessel with aportable data recording device.

The process for treating ballast water can comprise de-halogenating theballast water. In one embodiment, the process for treating ballast watercomprises drawing ballast water 402 onboard a vessel. The ballast wateris fed to one or more ballast tanks 220 on the vessel. Salt water ispiped from a salt water source 400 to one or more hypochloriteelectrolytic cells 130 to generate hypochlorite. The salt water sourcecan be a side stream 416 removed from the ballast water or any othersuitable source. An amperage is applied to the one or more hypochloriteelectrolytic cells 130 to produce hypochlorite within the salt water.The salt water comprising hypochlorite is introduced to the ballastwater to treat microorganisms in the ballast water. In one embodiment,the salt water comprising hypochlorite is added upstream of the ballasttanks to facilitate mixing of the hypochlorite and the ballast waterwithin a pipe.

The halogen content of the ballast water is measured with a means formeasuring halogen content 502. One or more reducing agents are added tothe ballast water in response to the measured halogen content tode-halogenate the ballast water prior to discharge from the vessel.

In one aspect of the process for treating and de-halogenating ballastwater, the means for measuring the halogen content 502 of the ballastwater comprises an oxidation/reduction potential analyzer. Optionally,the amount of reducing agent added to the ballast water is modulated tomaintain an oxidation/reduction potential measurement that indicatesexcess reducing agent is present in the ballast water.

In another embodiment of the process for treating and de-halogenatingballast water, the process further comprises measuring and recording theoxidation reduction potential of the combined ballast water andhypochlorite to confirm that excess halogen is present. Excess halogenin the ballast water will ensure that no microorganism will multiply inthe ballast water tanks. The halogen will be removed from the ballastwater by de-halogenation before discharge from the vessel. In oneaspect, the process can further comprise controlling the amount ofhypochlorite generated to ensure that excess halogen exists in theballast water.

In still another embodiment, the process comprises measuring andrecording process data. The process data can be later reviewed todetermine the effectiveness of the ballast water treatment orde-halogenation. Examples of process data which may be recorded includeballast water flow rate, amperage applied to the hypochloriteelectrolytic cells, cell voltage, oxidation/reduction potential of theballast water and side stream combined, and oxidation/reductionpotential of the ballast water prior to discharge from the vessel.

In yet another embodiment of the process, the amount of hypochloritegenerated may be controlled by measuring the flow rate of the ballastwater and modulating the amperage applied to the hypochloriteelectrolytic cells. This method of control is also known as flow pacing.To keep pace with the amount of ballast water drawn onboard the vesseland its inherent microorganism content, the amperage applied to theelectrolytic cells is function of the flow rate of the ballast water.

Alternatively, the amount of hypochlorite generated may be controlled inresponse to the total organic carbon content of the ballast water.Hypochlorite generated can be generated to maintain a weight ratio ofhypochlorite to total organic carbon content.

TEST EXAMPLES Example 1 Sodium Hypochlorite Mesocosm September 2004

The first test of the sodium hypochlorite generator/filtration treatmentsystem was started on Sep. 3, 2004. The experiment included achlorine/no filtration treatment and chlorine with filtration treatment.The target chlorination level was 4 mg/L. Initial chlorine levels forthe filtered treatment were 3.5 mg/L and 2.95 mg/L without filtration.There were 4 mesocosms (tanks) per treatment and 4 control mesocosms.The mesocosms were analyzed for Total Residual Oxidant (Cl₂ mg/L),culturable heterotrophic bacteria, chlorophyll a, and zooplankton at 5,24, 48, 120, and 240 hours following treatment.

Procedure

Total Residual Oxidant

Total Residual Oxidant (TRO) was measured as Cl₂ using a HachSpectrophotometer and Hach Colorimeter. DPD powder pillows were used forthe analysis. TRO measurements were after the initial fill and at all ofthe time points listed above. The 1500-gallon tank of raw seawater wastested for bacteria levels before the start of the experiment. Watersamples taken at the 5 time points were also tested for bacteria levels.

Culturable Bacteria

Bacteria colonies were cultured from known volumes of water to calculatecolony-forming units (CFU) per liter of water. Colonies were cultured onpetri dishes containing a growth medium suited for marine heterotrophicbacteria. The inoculated medium was analyzed for colony formation aftera few days at room temperature incubation.

Chlorophyll a

Water samples were also taken for chlorophyll a analysis. Chlorophyll ais an indicator for the presence of live phytoplankton. A known volumeof sample water was filtered through glass fiber filters with a poresize small enough to retain phytoplankton cells. The filters were frozenfor later analysis in our Seattle laboratory. Chlorophyll a wasextracted from the filters using acetone and then analyzed forfluorescence to determine the concentration in μg/L.

Mesozooplankton

Mesozooplankton were collected in Mystery Bay, using a 110 μm mesh net 1meter diameter the morning of the test. Enough were collected to achieveapproximately 150 mesozooplankton per liter. A Stempel pipette was usedthree times to collect a randomized 5 ml sample of the mesozooplankton“soup”. The densities, counted using a dissecting scope, were used tocalculate how much of the “soup” was needed for the 1500-gallon tanks toachieve 150 mesozooplankton per liter. The calculated amount of soup waspoured into the tank and allowed to settle for at least an hour to letzooplankton acclimate. Three preliminary samples were collected out ofthe 1500-gallon tank after mixing. These were used to check calculationand to see the effects of the pumps. Sampling periods formesozooplankton were 5, 24, 48, 120, and 240 hours. Samples werecollected out of the 72-gallon mesocosms using a 1-liter Nalgene bottleafter thoroughly mixing the contents of the mesocosm. Liter sample wasfiltered through a 73 μm sieve and placed in counting tray.Mesozooplankton counted were placed into one of eight generic categoriesand then by state; live, dead (absolutely no response to poking) ormoribund (internal movement and no flight response to needle poke).

Results for Example 1

Total Residual Oxidant (TRO) levels declined steadily for the durationof the experiment. (FIG. 3). TRO in the nonfiltered test tanks droppedmore than the filtered test tanks in the first 5 hours and then the TROdissipated equally for the remaining time points.

Bacteria were greatly reduced in both treatments and showed minimalrebound over the 10 days of the experiment. There was a slight reboundof bacteria in the treatment without filtration.

Chlorophyll a is an indicator of phytoplankton. In the treated seawater,Chlorophyll a levels were at or below the detection limit starting withthe 5-hour time point and continued to drop for both of the treatments.

In the control tanks, chlorophyll a levels declined over the duration ofthe experiment, likely due to the absence of light since all of themesocosms were covered.

After the first treatment trial it was concluded that no statisticaldifference could be found between the two treatments, at all time pointsand states. The difference between the control and treatments was highlysignificant. Some mesozooplankton were still able to get through the 50μm filter, all were dead except for 2 organisms.

Example 2 Sodium Hypochlorite Mesocosm October 2004

The second test of the sodium hypochlorite generator/filtrationtreatment system was started on Oct. 12, 2004. Two experiments wereperformed. The first experiment compared two treatments,filtration/chlorination (˜1.0 mg Cl₂/L) versus filtration only. Thesecond experiment compared a chlorination dose of 1.0 mg Cl₂/L with adose of 1.6 mg Cl₂/L. Each experiment included 4 mesocosms per treatmentand 4 control tanks. The mesocosms were analyzed for Total ResidualOxidant (TRO) (mg Cl₂/L), culturable heterotrophic bacteria, chlorophylla, and zooplankton at 5, 24, 48, and 240 hours following treatment.Culturable phytoplankton was enumerated in the first experiment. Sampleswere also collected at 5 hours for nutrient and total organic carbon(TOC) analysis. The temperature in the mesocosms fluctuated between12.0° C. and 14.0° C.

Procedure

The procedure for Example 2 was the similar to the procedure used inExample 1 except for the phytoplankton technique.

Phytoplankton Most Probable Number Technique

During the first October experiment we tested the use of the MostProbable Number (MPN) technique, a dilution based culture method, toenumerate viable phytoplankton cells after treatment. Phytoplanktonsamples were collected from each treatment (control, filtered, andfiltered and chlorinated) at four time points (5, 24, 48, and 240hours). Each sample was filtered onto a glass fiber filter, and thisfilter (containing phytoplankton cells) was used to inoculatephytoplankton growth medium (f/2) over a dilution series. Theinoculations were then transferred to incubators set to optimize growth(12:12 light:dark cycle, 13° C.). The pattern of growth over thedilution series allows for a calculation of the MPN, an estimate of thenumber of viable phytoplankton cells per L. Using this technique we candetermine the effectiveness of a particular treatment at reducing thenumber of viable phytoplankton by comparing control andtreatmentabundance estimates.

Results

Total Residual Oxidant—The goal of the filtration with chlorinationtreatment was to dose to an initial TRO level between 0.5 and 1.0 mgCl₂/L. The actual dose achieved had an average TRO of 1.11 mg Cl₂/L atthe initial filling of the mesocosms (FIG. 4). This TRO declined 54% inthe first 5 hours to a TRO of 0.51 mg Cl₂/L. TRO degradation slowed withtime and completely disappeared by 240 hours. TRO for the chlorinationonly treatments of the second experiment showed a similar degradationcurve. The goal of the chlorination only treatments was to dose with aninitial TRO of 1.0 and 1.5 mg Cl₂/L. The actual dose averages were 0.94mg Cl₂/L and 1.61 mg Cl₂/L TRO. Highest percent reduction of TROoccurred with the lowest TRO dose.

Culturable Bacteria were initially reduced in all 3 of the chlorinatedtreatments at 5 hours. Although slightly suppressed, bacteria in thechlorinated treatments rebounded to levels higher than the controls by240 hours. The filtration only treatment showed negligible reduction inbacteria at 5 hours with levels equal to the control treatment atsubsequent treatments.

Mesozooplankton—Chlorine plus filtration had an immediate effect uponthe zooplankton, reaching a 95% mortality at 5 hours and completemortality at 24 hours. By 48 hours the high chlorine treatment resultswere similar to the filtration with chlorination treatment. At 5 hoursthe filtration with chlorine treatment had no live organisms per L,there were only 1-2 moribund organisms per L at this time. The percentdead of the two controls were similar except for the 48 hours sample.

Chlorophyll a is an indicator of phytoplankton biomass. The filtrationwith chlorination treatment showed the greatest initial reduction inchlorophyll a compared with the chlorination only treatments. At 5 hourschlorophyll a levels were reduced by 98% for the filtration withchlorination treatment when compared to the control treatment. Thefiltration only treatment showed slight reduction when compared with thecontrol treatment. In the control tanks, chlorophyll a declined over theduration of the experiment, likely due to the absence of light since allof the mesocosms were covered.

The phytoplankton culture (MPN) technique shows that the number ofviable phytoplankton cells was greatly reduced by filtration compared tothe control. Some of the inoculations showed positive growth over theentire series of dilutions, thus allowing us to only estimate the MPN asgreater than or equal to result. It appears that filtration removes asmuch as 50% of the viable phytoplankton from the mesocosms. Thereduction of viable phytoplankton was more dramatic when water wastreated with the combined filtration and chlorination system. Numbers ofviable phytoplankton were reduced 99% by this treatment compared to thecontrol.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims.

The invention claimed is:
 1. A process for treating ballast watercomprising: drawing ballast water onboard a vessel; feeding the ballastwater to one or more ballast tanks; piping salt water from a salt watersource to one or more hypochlorite electrolytic cells; applying anamperage to the one or more hypochlorite electrolytic cells to generatehypochlorite within the salt water; controlling a rate of hypochloritegeneration by adjusting the amperage applied to the one or morehypochlorite electrolytic cells based on at least one of: a flow rate ofthe ballast water measured by a flow meter, and a total organic carboncontent of the ballast water measured by a total organic carbonanalyzer; introducing the salt water comprising hypochlorite to theballast water; measuring the halogen content of the ballast water with ameans for measuring halogen content; adding reducing agent to theballast water in response to the measured halogen content tode-halogenate the ballast water prior to discharge from the vessel. 2.The process of claim 1 wherein the salt water source comprises a sidestream removed from the ballast water.
 3. The process of claim 1 whereinthe reducing agent is selected from a group consisting of: sodiumsulfite, sodium metabisulfite, sodium bisulfite, sulfur dioxide, andsodium thio sulfate.
 4. The process of claim 1 wherein the step ofintroducing the salt water comprising hypochlorite to the ballast watercomprises: introducing the salt water comprising hypochlorite upstreamof the of the ballast water tanks.
 5. A process for treating ballastwater comprising: drawing ballast water onboard a vessel; removing aportion of the ballast water to form a side stream; piping the sidestream to one or more hypochlorite electrolytic cells; applying anamperage to the one or more hypochlorite electrolytic cells to generatehypochlorite within the side stream; controlling a rate of hypochloritegeneration by adjusting the amperage applied to the one or morehypochlorite electrolytic cells based on at least one of: a flow rate ofthe ballast water measured by a flow meter, and a total organic carboncontent of the ballast water measured by a total organic carbonanalyzer; reintroducing the side stream to the ballast water; feedingthe ballast water to one or more ballast tanks; measuring theoxidation/reduction potential of the ballast water; adding a reducingagent to the ballast water to de-halogenate the ballast water inresponse to the measured oxidation/reduction potential; and dischargingthe ballast water from the vessel.
 6. The process of claim 5 wherein thereducing agent is selected from a group consisting of: sodium sulfite,sodium metabisulfite, sodium bisulfite, sulfur dioxide, and sodiumthiosulfate.
 7. The process of claim 5 wherein the amount of reducingagent added to the ballast water is modulated to maintain anoxidation/reduction potential measurement that indicates excess reducingagent is present in the ballast water.
 8. The process of claim 7 whereinthe oxidation/reduction potential is maintained at less than about 200mV.
 9. The process of claim 8 wherein the oxidation/reduction potentialis maintained at about 0 mV.
 10. The process of claim 5 furthercomprising measuring and recording the oxidation reduction potential ofthe combined ballast water and side stream to confirm that excesshalogen is present.
 11. The process of claim 5 further comprisingmeasuring and recording process data.
 12. The process of claim 11wherein the process data comprises one or more parameters selected froma group consisting of: ballast water flow rate, amperage applied to thehypochlorite electrolytic cells, voltage in the hypochloriteelectrolytic cells, oxidation/reduction potential of the ballast waterand side stream combined, and oxidation/reduction potential of theballast water prior to discharge from the vessel.
 13. The process ofclaim 5 comprising controlling the amount of hypochlorite generated toensure that excess halogen exists in the ballast water.
 14. The processof claim 5 further comprising measuring the oxidation/reductionpotential of the ballast water at one or more sites selected from agroup consisting of: within the one or more ballast water tanks,downstream from the ballast water tank, upstream from one or moreballast water discharge pumps, downstream from the ballast waterdischarge pumps, prior to the addition of reducing agent, and after theaddition of reducing agent.
 15. The process of claim 14 furthercomprising recording the oxidation/reduction potential of the ballastwater at timed intervals.
 16. The process of claim 15 further comprisingproviding the recorded oxidation/reduction potentials to a regulatoryagency.
 17. The process of claim 5, further comprising: removing aportion of seawater from a secondary seawater source to form a secondaryside stream; and piping the secondary side stream to the one or morehypochlorite electrolytic cells.